This application relates generally to a process and apparatus for manufacturing non-woven material and the product thereof.
There are a number of applications wherein it is desired to form and feed various types of tubular material. These applications primarily relate to the formation of the tubular material from various plastic materials. One such application is the manufacturing of plastic tubular pipe. In the manufacture of such pipe, various systems have been devised wherein liquified material may be fed to a forming device which accepts the material and feeds it along a path during solidification thereof to ultimately form the pipe. One of the known means of accomplishing this operation is to use a series of belts which have a substantial longitudinal dimension and are of such a width that the use of a substantial number arranged in a circular fashion will approximate a circle. As can be seen, the use of such equipment involves extensive apparatus and results in a relatively expensive machine. Additionally, the use of so many individual units precludes the possibility of having a perfectly smooth structure which has a consistent width dimension.
There has also been proposed a system wherein biaxially oriented thermoplastic resinous film is prepared by extruding a tube and stretching same by a rotating torus whereby the film is oriented.
Another field of endeavor wherein such a structure is proposed is in the field of the production of non-woven webs of polymeric materials. In a specific manufacturing technique, these materials are developed through the use of an annular extruding device which feeds a molten material through an extrusion slot with a quenching step solidifying the material shortly after it exits from the extruder. This process requires some means for moving the material away from the extruder after solidification.
If the above extruder device contains an annular slot, the material will be formed in a tubular fashion and must be removed from the extruder in that geometric form even though it may be slit subsequently to form a flat sheet. A proposed way for removing this material is to have the tubular solidified material pass over a mandrel with some means for exerting a pulling force so as to stretch the extrudate, fibrillate, draw and collect the tubular material. A major problem involved in this type of operation results from the friction created between the material and the mandrel itself. This friction imposes severe limits on the speed at which the material may be produced and therefore, greatly reduces the efficiency of the operation.
A further problem involved in producing web material is the structural strength which the web material may have in both the machine direction and the transverse direction. Normal web structure has a filament alignment which generally parallels that of the machine direction. This, of course, means that the structural strength is stronger in the machine direction than it is in the transverse direction. Therefore, in any type of multiply operation, it does not do any good to merely lay one continuously produced web over another in the same direction since such an operation will merely be increasing the already existing strength in the machine direction without improving the transverse strength of the web. Attempts have been made to overcome this problem by overlapping the material. However, it is obvious that overlapping in order to obtain a 90.degree. filament cross-alignment would be very tedious and almost impossible to produce by a continuous operation. Additionally, overlapping marks are visible which precludes use for aesthetic as well as practical reasons. Attempts have been made to provide such an overlapping by a spiral winding technique in order to get an angle between the filament alignment of the webs in the multiply structure. However, such overlapping is not feasible with light and drapy materials over any large diameters, expecially when a low number of plies are used since it produces extra thick portions and destroys the continuity of the multiply material.
Some known experiments have attempted to scramble the filaments in order to obtain some type of equal strength in the machine direction and in the transverse direction, but this has not proven to be effective, nor has it produced a practical product since it also includes the overlapping of the webs with resultant discontinuities.
Many of the above discussed approaches are shown in the following U.S. Patents:
______________________________________ 3,905,736 Bringham 3,342,657 Dyer 3,472,924 Sederlund et al 3,711,231 Chess et al 3,539,666 Schirmer 3,403,203 Schirmer 3,717,541 Schirmer 3,581,344 Sederlund et al 2,943,356 Rasmussen 3,322,613 Rasmussen 3,354,253 Rasmussen 3,409,495 Rasmussen ______________________________________
The present invention, for the first time, provides an effective alignment of filaments at an angle to the machine direction of the resultant web through a unique cutting procedure. The resultant web may then be plied or overlapped without any of the previously existing problems of discontinuities.
It should be noted that, when providing the multiply product, the webs may be bonded in any of the well known ways such as thermal bonding, sonic bonding, mechanical bonding by needle punching or stitch bonding or sewing, or adhesive can be used to make all plies adhere together.
An object of this invention is to produce a continuous web material having an effective alignment of filaments at an angle to the machine direction of the web being produced.
Another object of this invention is to provide a thermoplastic web of indeterminate length having substantially parallel filament alignment with the alignment being at a predetermined angle to the longitudinal axis of the web.
Yet another object of this invention is to provide a multiply structure having multiple webs wherein the effective alignment of filaments in at least one web is at a substantial angle to the effective alignment of filaments in the remaining webs.